The present invention relates to a control circuit for an electrically controlled device. In particular, the invention relates to controlled devices having an arbitrary, for example a non-linear or, respectively, a linear but non-continuous response curve or map of response curves.
Although the present invention is not restricted to valve devices in hydraulic systems, but may be applied to different types of controlled devices, such as transistors or general control systems and thus is applicable to a broad variety of systems using a controlled device which receives an electrical input signal and delivers an electrical, mechanical, hydraulic or pneumatic output magnitude for actuating a power member, wherein input and output magnitudes are correlated in a non-linear relation, the embodiments of the present invention explained below relate to a hydraulic system, as preferably proportional directional solenoid valves exhibit a high grade non-linear response which makes necessary a correction of the response curves.
The art contains a number of correction circuitries, e.g. a control circuit for a valve (German 29 16 172) in which the desired input value is digitalized, correction values correlated to the desired value are read out from a read-only memory, the correction values are added to the desired value and the corrected desired signal is converted again to an analog magnitude. Furthermore, different circuitries for controlling valves make use of microprocessors including read-only memories or table stores to provide correcting the response curve.
An object of the present invention, is to ensure a desired response of a controlled device by using means of minimum expenditure. A further object is to recognize the relationship between the input and output signal of the controlled device in a shortest possible time to handle the correction quickly and efficiently.